The present invention relates to an expanding collet chuck having radially extending clamping parts with counter guiding surfaces, whereby the clamping parts cooperate with a mandrel having guiding surfaces.
Expanding collet chucks of the aforementioned kind connect the tool with the tool holder during machining steps. They usually not only provide support for the working forces, but also automatically adjust. i.e., center the tool during the clamping process into a certain position that is necessary for a machining process with satisfactory results. A collet chuck is always usable for different shapes and dimensions of tools within a certain range. For turning and grinding or polishing of outer surfaces of tools, the tools are clamped with their semi-finished or finished bores onto the collet chuck. The clamping force acts radially from the inside to the outside. The collet body several receiving cutouts that are arranged equally spaced about its circumference, having arranged therein wedge-shaped, flat clamping parts, that are radially adjustable in the receiving cutouts. The mandrel which has a circular cross-section is moved towards the inside during clamping and thereby presses, due to its conical shape, the clamping parts that are connected to one another via holding springs toward the outside. This arrangement, however, allows only for little truth of concentricity.
It is therefore an object of the present invention to provide a collet chuck of the aforementioned kind with which a truth of concentricity with a deviation of less than 10.sup.-2 mm may be achieved.